In the present scenario, lead foam is prepared by coating lead over the copper foam, which has good conductivity, and a uniform three-dimensional reticulate structure. However, the stability of foam in its application in the lead-acid battery system is affected due to the reaction of electrolyte (sulphuric acid) with the copper on account of pores. The present invention forefend the contact problem and interaction of electrolyte etc., which gives good performance because of the method of preparation of lead foam excluded the copper. Till date, the total scenario of metallic foam and the available technology for the preparation of metallic foam are:
Patent No.Reg. date.InventorField of searchU.S. Pat. No.Apr. 22, 1997Thomas75/4155,622,542et al.,428/593U.S. Pat. No.Dec. 9, 2003Formmeyer164/79,6,659,162 B2et al.,428U.S. Pat. No.Jun. 18, 1974Niebyski75/20,3,816,952et al.,138U.S. Pat. No.Feb. 28, 1978Perugini428/311,4,076,888et al.,428/308U.S. Pat. No.Dec. 27, 2005Kelly429/121,6,979,513 B2et al.,429/236U.S. Pat. No.Oct. 15, 2002Popoola419/2,6,464,933 B1et al.,427/247, 455U.S. Pat. No.Feb. 5, 1974Niebyski75/20F,3,790,365et al.,20R, 86U.S. Pat. No.Jun. 3, 1980King204/149,4,206,031210/49U.S. Pat. No.Sep. 18, 1990Babjaketal.70/20F, 419/2,4,957,543428/614U.S. Pat. No.Jul. 22, 2008Ayer419/2, 8,7,402,277 B2et al.,9 427/191U.S. Pat. No.Nov. 24, 2009Schrorers164/79,7,621,314 B2et al.,148/403U.S. Pat. No.Dec. 15, 1959Grandey264/44,2,917,384et al.,419/37
References may be made to U.S. Pat. No. 5,622,542 Thomas et al., that identifies the process for producing metal foam from a composite capable of forming foam by heating the matrix above its liquid temperature and then foamed by injecting gas in to the material to form a particle stabilized metal foam. Foam is prepared by liquid—gas phase technique.
The U.S. Pat. No. 6,659,162 B2 by Frommeyer et al., discloses the processes for producing large area integral metal foam by adding a blowing agent to a metal melt is described. This method follows continuous injection of blowing agent into a roll nip to form metal foam, and claims that the gas and solid released at room temperature and is fully foamed to form large area integral metal foam. Foam is prepared by adding blowing agent to the molten metal to form foam.
In the U.S. Pat. No. 3,816,952 by Niebyski et al., blowing agent materials such as titanium hydride, hafnium, zirconium, metal hydride etc., were mixed with the molten metal in order to increase the viscosity, gases such as air, oxygen, nitrogen, argon etc., were injected in to the melt to prepare metal foam, in particular the aluminum foam. Foam is prepared by adding blowing agent to the molten metal.
The U.S. Pat. No. 4,076,888 by Perugini et al., discloses preparation of metal/metal ceramic foam (sponge). This process starts from a plastic sponge with three dimensional cellular structures and coating the metal or ceramic-metal composition by using techniques such as molten spray deposition, galvanic codeposition, and evaporation under vacuum or reactive sputtering for selected metals. In this patent foam is prepared by molten spray technique under vacuum technique. The patent claims the unaltered filiform morphology.
The U.S. Pat. No. 6,979,513 B2 by Kelley et al., used the carbon foam as grid and pasting chemically active material in the pores of carbon foam for making positive and negative plates to be used in lead-acid batteries. This method claims that the carbon foam is used as current collector which results poor adherence of active material to the substrate.
The U.S. Pat. No. 6,464,933 B1 by Popoola et al., describes the formation of metal foam by introducing metal powder supply along with foaming agent into a propellant gas which form gas/particle mixture stream. The mixture is then projected over a metallic substrate at sonic velocity. The coated substrate treated thermal excursion effective to active expansion of the foaming agent there by making metal foam. The technique uses thermal excursion using gas/particle mixture stream, which is a high temperature process.
The U.S. Pat. No. 3,790,365 by Niebylski et al., describes that by decomposing one or more blowing agents in a molten metal with blowing gas. This method uses expansion and cooling repeatedly with intermediate stirring and adding foaming agents to form metal foam. This method uses blowing agent with blowing gas in a molten bath for metal foam development.
The U.S. Pat. No. 4,206,031 by King et al., describes a methodology for preparation of metal foam using electrolytic action that exposed in the liquid metal results in metal foam. The unique claim by author is that the formation of thick, creamy foam on upper surface of liquid metal. The author also described the foam generating apparatus, which explains the apparatus having two electrodes exposed to incoming metal liquid got foamed by electrolytic action. The author uses thick, creamy foam formation on the upper surface of the molten metal.
The U.S. Pat. No. 4,957,543, Babjak et al., provide a methodology to make nickel foam, where an open cell foam structure is placed in a nickel carbonyl gas chamber. The chamber will be heated to a temperature where the gas decomposes to nickel will results in nickel foam. The method uses reducing the metal carbonyl to pure metal foam, which is a high temperature processing technique.
The U.S. Pat. No. 7,402,277 B2, Ayer et al., present a method of foaming metallic foam by using cold spray process, in that the mixture of metal particle and foaming agent are mixed together and spray coated on a substrate which to form unexpanded metallic layer. The obtained substrate is subjected to heat treatment above decomposition temperature there-by made expanded metal foam. The technique uses spray process on a substrate and using high temperature heat treatment process to obtain expanded metal foam
The U.S. Pat. No. 7,621,314 B2, Schrorers et al., confirm the production of metallic foams from bulk-solidification of alloys. It describes the method of making the amorphous metallic foam and the apparatus which has heating and cooling zone along with gas injection design. The patent uses heating and cooling with gas injection to form metal foam
The U.S. Pat. No. 2,917,384, Max Ferdinand Grandey et al., develop foams of nickel, chromium, aluminum, cobalt, iron, titanium, nichrome, stainless steel from its metal powders mixed with foamable resin such as silicone, isocyanate, polyester where condition desires. The mixture of metal and resins will be treated under reduced or inert atmosphere at the melting temperature to obtain corresponding metal foams. Powder metallurgy technique is used in preparing metal foam
The Metal Material and Metallurgy Engineering, 2011, 04 by QuWen-chao et al., discloses regarding the preparation of lead foam is by electro-deposition method. The author uses polyurethane foam as substrate for developing lead foam. The stage one goes along with coating of copper on substrate using electroplating technique with current density of 3.0 A/dm2, polar distance of 3.5 cm, and galvanized for about 35 min which is forming thick copper coating over the surface. This will as similar as copper foam and it was followed by the second step coating of lead plating with a current density of 3.0 A/dm2, at temperature of 25° C. and galvanization time of 30-40 min. This results in the formation of lead over copper coating.